Openness in the world of automation means being able to buy a variety of products from a variety of vendors and have everything work together seamlessly. To be truly open, however, means the network or platform is accessible to anyone and there is more than one source of enabling technology, i.e., microprocessors and application code. Openness promises significant savings in both time and money. However, recent attempts at openness have not lived up to the promise.
The current market trend is to move to an open, modular architecture controller that will include a horizontal integration of the currently existing fragmented technologies. Currently, most computerized numerical control (CNC), motion and discrete control applications incorporate proprietary control technologies. There are numerous difficulties associated with using proprietary technologies. These include such things as vendor dictated pricing structures, non common interfaces, higher integration costs and the requirement of specific training for troubleshooting and operation. Separate controller elements, a modularity concept and higher level requirements for various elements of an open modular architecture controller are becoming a necessity in a growing number of industries.
The expected benefits of having open and modular architecture controllers include reduced initial investments, low life cycle costs, maximized machine uptime, minimized machine downtime easy maintenance of machines and controllers, easy integration of commercial and user proprietary technologies, plug and play of various hardware and software components, efficient reconfiguration of controllers to support new processes, incorporation of new technologies and the integration of low cost, high speed communication in machining lines for transferring large amounts of data.
The technology that can enable the new trends and requirements supplied by the personal computer (PC) standards connectivity and communications, the `Plug and Play` standard for PC cards is becoming a way of life. Within the control industry, the PC is becoming increasingly recognized as a viable technology that will enable the required flexibility and performance.
In today's large automation market, there is a growing number of PC board manufacturers that produce a variety of boards. These boards are targeted towards automation implementation that use the PC and the control platform. Since automation data networks implements a proprietary technology that are not very open for `Intranet communication.`
Traditional Automation and Control Layer networks are typically medium sized and function to connect PLCs or PCs to related devices within cells or throughout the plant. These networks send small to medium sized packets of data repetitively and have millisecond response times.
A high level block diagram illustrating an example prior art proprietary control network including proprietary programmable logic controllers, sensors and I/O devices is shown in FIG. 1. A proprietary network 33 (e.g., Fieldbus) forms the core of the automation control system. Connected to this network are programmable logic controllers (PLCs) 34 which as also proprietary. Connected to the PLCs 34 are the sensors and other I/O devices 32. The proprietary PLCs implement the Automation and Control Layer functionality and the sensors and I/O devices implement the Information and Device Layer.
Traditionally, a single manufacturer was able to provide the necessary connectivity with its own network and PLC products and those of qualified third parties. This is not a trivial task as the lead manufacturer must assist these third parties throughout the development process and even after products start to ship. The lead manufacturer, typically the one making the controllers, assumes network ownership by providing specifications, enablers, e.g., chips and software, and test suites for compliance and interoperability.
Examples of previous attempts at openness in the field of industrial networking include the Fieldbus and manufacturing automation protocol (MAP). Both buses are open networks that are not currently meeting user expectations. The MAP bus is not in widespread use today and most vendors have dropped development of MAP products. One of the problems is that although the products have been designed in accordance to a standard specification, many versions of a specification are in use at any one time. In addition, many so called open products require unique configuration software which is only available from the manufacturer of the product. Thus, it becomes a difficult task to get products from different vendors, all built to different versions of a specification, to interoperate together correctly.
Fieldbuses are a special form of local area networks dedicated to applications in the field of data acquisition and the control of sensors and actuators in machines or on the factory floor. Fieldbuses typically operate on twisted pair cables and their performance are optimized for the exchange of short point to point status and command messages. Numerous other Fieldbuses are in existence such as Filbus, Bitbus, FIP, CAN and Profibus standard networks.